A valve control mechanism for intake and exhaust valves of internal combustion engines is provided. The valve control mechanism has at least one piezo element, at least one valve element operated thereby, and at least one adjustment piston. Inflow and outflow of a pressure medium to the adjustment piston is controlled by the valve element. The adjustment piston is moveable by the pressure medium, against a counter pressure, for opening an intake or exhaust valve.
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1. A valve control mechanism for intake and exhaust valves of internal combustion engines, comprising:
at least one piezo element; at least one valve element, said valve element operated by said at least one piezo element; at least one adjustment piston, wherein inflow and outflow of a pressure medium to said at least one adjustment piston is controlled by said at least one valve element, and wherein said at least one adjustment piston is moveable by said pressure medium, against counter pressure, for opening an intake or exhaust valve; and a pressure line for supplying said pressure medium, said pressure line connected to a pressure medium source, wherein said pressure line is connected to a surge chamber disposed in front of said adjustment piston when said valve element is in an open position, wherein said connection between said pressure line and said surge chamber is closed when said intake and exhaust valve is in a closed position, and wherein a tank line is simultaneously opened and the pressure medium is displaced through the adjustment piston into the tank line.
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The invention relates to a valve control mechanism for intake and exhaust valves of internal combustion engines having at least one adjustment element with which the intake or exhaust valve is opened and closed.
In standard internal combustion engines, the control of the lifting movement of the intake and exhaust valves takes place through one of the crankshafts in a speed-ratio of 2:1 relative to the driven camshaft. The lifting curve of the valve is proportional to the curve of the cam for the entire sphere or reach of the performance graph and therewith unchangeable. The closing point of the intake valve is, conditional on the variable flow velocity in the exhaust pipe, not optimally situated. The intake valve's opening point, likewise, can also not be optimally situated. The data for the best possible (ideal) operating capacity of the combustion chamber at a high number of revolutions and of the cylinder-exhaust contents at a low number of revolutions and in idle are diametrically opposite. The opening point for the exhaust source is usually selected so that the exhaust release is minimized and the gas is in the position to perform the maximum amount of work.
Through avoidance of the aforementioned adjustments, there are always compromises, valve control mechanisms are developed, in order to be able to affect and change control-reaction time, stroke response of the intake/exhaust valves as a function of the engine speed, which load and other limiting qualities control and change. The operation of the valve lift can be affected or changed therewith through variation of the phase-relationship of the valve lift or the valve-opening time. Such measures can be used singly or in combination, on the one hand, in order to reduce fuel consumption and emissions of spark-ignition engines, while on the other hand, to improve the flow of the torque and to achieve the maximum power or output. A further advantage is the possibility that the sucked-in air mass can be affected by changing the cross-section of the valve opening, thereby making possible a choke-free load control without a throttle valve or flap.
Through multi-valve technology, such wiring can be undertaken, that the sucked-in load flows only over an intake valve, by which the air mass is affected. A cylinder shutoff, through the control of the intake/exhaust valve, likewise can be involved, whereby the fired cylinders can work most efficiently through the masking of the injection and combustion air. With modern engine electronics, the cylinder shutoff can be cyclically (selectively changed, in order to avoid the cooling-off of the cylinder wall.
The possibilities described above for controlling and altering of parameters are grouped together under the concept "variable valve control mechanisms." The manner of valve operation varies between direct and indirect operating systems.
With indirect operating systems, two solutions are known, namely the use of a variable camshaft or a variable intermediate element. With direct operating systems, basically three possibilities are known, which result in either a hydraulic, pneumatic or electric operation of the valve. A camshaft is not used in this situation.
In the hydraulic system, energy is saved, similar to a so-called Common Rail System and through fast-acting magnet valves or servo valves of the set piston surfaces, the energy is fed or discharged, by which the intake/exhaust valves are operated. Such systems are known for their use in long-running diesel engines.
The invention addresses the underlying problem of developing the type of valve control mechanism which operates simply and reliably at high switching frequencies, instead of an expensive servo valve, so that the valve control mechanism is also useful for high rotary internal combustion engines.
This problem is resolved by the type of valve mechanism with the specific charateristics of the invention namely, at least one piezo element; at least one valve element that is operated by said at least one piezo element; and at least one adjustment piston, wherein inflow and outflow of a pressure medium to the at least one adjustment piston is controlled by the at least one valve element, and wherein the at least one adjustment piston is moveable by the pressure medium, against the counter pressure for opening an intake or exhaust valve.
With the valve control mechanism which is the subject of this invention, a piezo electric actor is employed as an adjustment element. With this, a lightweight valve element is operated, which controls the inflow and outflow of the pressure medium to and from the adjustment piston, by whose lift the intake and exhaust valves of the internal combustion engine are opened and closed. Piezo electric actors convert electric voltage directly into movement and energy. The conversion of the electric input quantity into a mechanical output quantity occurs extremely quickly. By way of example, an adjustment lift of 40 μm (0.04 mm) can occur at a regulating time of 50 μs (0.00005 sec). The dissociation of the adjustment path, or movement, is possible in smaller electric currents of nanometers (0.0001 mm). Adjustment force is reached in kilo-newtons, that is to say, it acts as a correcting element with very high mechanical rigidity.
In the high-dynamic area, on the one hand, the availability of the suitable energy amplification is an essential prerequisite, in order to synchronize the current-running and the reaction of the intake and exhaust valves. On the other hand, the flow-through cross-section of the seating valve has to be adequately large in dimension. This results in an advantageous development of the valve control mechanism of the present invention by increasing the lift in value, for which the available adjustment movement of the piezo electric transformer does not suffice. Therefore, an adjustment-movement enlarger, or increaser, is used, which advantageously works by the principles of levers and which can increase the useable adjustment movement or action of the valve element, for example, to a factor of ν=10.
With the valve control mechanism of the present invention, the opening and closing points of the intake and exhaust valves can be determined as required.
Further characteristics of the invention are presented in the additional claims, the specification and the illustrations.
The invention is illustrated with the aid of the several embodiments shown in the accompanying figures:
With the aid of
The valve control mechanism described below makes possible high control frequency, so that this valve control mechanism also can be used with high rotary internal combustion engines.
The valve control mechanism according to
If the piezo element 1 is again currentless or dead, the valve element 3 will be returned to its closed position illustrated in
The piezo element 1 can be driven at very high frequencies, so that the described opening and closing operation of the intake/exhaust valve 30 can take place at the required high control frequency. The valve control mechanism is therefore suitable for internal combustion engines which run at high speeds. In the described manner, similar valves 30 of an internal combustion engine 26 can be operated.
The intake/exhaust valve 30 is maintained in the open position and in the closed position, respectively, over a period of time as described above. In this manner, here are four cyclical, repeating working phases for the intake/exhaust valve 30, namely, opening, held-open, closing, and held-closed.
The set piston 15 is found in the area between the two-way seating valve 9 and the piezo element 1. If the piezo element 1 is charged and therefore elongated, the lever 33 will be swung in a counterclockwise direction around its vertical axis toward the horizontal axis of the piezo element 1. In this manner, the stem or rod 2 is shifted downwards, whereby the valve element 3 is shifted into the open position by the force of the compression spring 6. The pressure line 7 is opened, so that the pressurized hydraulic medium can flow over the restrictor 11 in the surge chamber 14. The set piston 15 is thereby shifted downwards. The valve shaft 22 is shifted via the rod or plunger 19 and the cupping rod 20 under the force of the compression spring 21, so that the valve head 23 is raised or lifted from the valve seating and the intake/exhaust opening 24 in the internal combustion chamber 25 is released. In this open position the piezo element remains charged. In this static operation, a nearly powerless retention of the driven position of the set piston 15 is possible. As soon as the piezo element is again currentless or dead and thereby shortened, the valve element 3 is moved by means of the pressure spring 6 to its closed position and the connection from the pressure line 7 to the surge chamber 14 is broken. The surge chamber 14 is now only connected to the tank by the restrictor 13. The lever 33 is swung or pivoted in a counterclockwise direction around the axis 36 over the rod 2. The pivoting movement ends with the closing of the valve element 3. The valve shaft 22 is shifted upwards by the pressure spring 21, whereby the piston 15 is shifted upward via the cupping rod 20 and the rod 19. The hydraulic medium found in the surge chamber 14 is expelled or driven out to the tank through the restrictor 13 and the tank line 12 in the described manner. In this closed position, the piezo element remains uncharged in accordance with engine management.
The cupping rod 20 is found in an intake area 37 of the internal combustion engine 26. The valve housing 5 is fastened to the internal combustion engine 26. The intake area 37 is closed by the valve housing 5.
In that the piezo element 1 is arranged in the area near the two-way seating valve 9 and the set piston 15, the valve housing 5 has only a small height. Because of this, the set piston 15 also is arranged in the area near the two-way seating valve 9. The lever 33 serves as a transmission lever, which transmits the very small course of the piezo element 1 over the lengthened lever arm in a sufficiently large displacement course of the rod 2.
Upon opening of the intake/exhaust valve 30, the piezo element 1 is charged and is thereby enlarged. The two-armed lever 33 is thereby swung around the axis 36 in a counterclockwise direction, whereby the rod 2 is displaced under the force of the compression spring 6, until it fits tightly on the other valve seating 42. By this process, the tank line 12 is closed, so that the charged medium flowing through the pressure line 7, with the exception of the supply line, arrives in the surge chamber 14. By this process, the front face 16 of the set piston 15 is loaded with pressure medium, so that it is shifted below in the described manner and displaces against the rod 19 and the cupping rod 20 of the valve shaft 22. In this way, the intake/exhaust valve 30 is opened in the described manner and in case of need, is maintained in an opened position.
Upon closing of the intake/exhaust vale 30, the piezo element 1 is switched to currentless and shortens itself to its unsprung length. The valve element 3 is shifted by the compression spring 6 to the higher valve seating 41, whereby the pressure line is closed and the tank line is opened. In this manner, the hydraulic medium can be emptied out of the surge chamber 14 through the supply line 10 in the tank line 12. Through the release of pressure from the surge chamber 14, the intake/exhaust vale 30 is closed in the previously described manner and in case of need, is maintained in a closed position.
The lower valve seating 42 of the three-way valve 9' is provided with an insert 43 (FIG. 11), that is held in a wider insert. It is pressed in a mounting area 45 of the valve housing 5. The free end of the insert 44 is inwardly flanged, whereby the insert 44 is held in place.
The three-way valve 9' constitutes a changeover valve. The valve element 3 accordingly has two valve portions 83 and 85, with which it alternately fits closely on the higher valve seating 41 and the lower valve seating 42. The higher seating portion 83 is constructed in partial ball shape in the illustrated preferred embodiment but can also have a conical shape. The valve portion 83 has somewhat of a half-ball shape. On the valve portion 83, a shoulder is connected, on which the compression spring 6 by its upper end is suspended. The shoulder 84 widens itself into a conical shape from the upper valve portion 83. In the transition from the shoulder 84 in the upper valve portion, a step or ridge is formed. The difference in diameter between the shoulder 84 and the valve portion 83 corresponds to the doubled wire gauge of the compression spring 6. In this manner, the upper end of the compression spring does not protrude radially across the valve portion 83. If the shoulder 84 is constructed in a conical shape, the compression spring 6 also has a conical shape. The upper end area of the compression spring 6 fits against the wall or surface of the shoulder 84. If the shoulder 84 and the compression spring 6 are constructed in a conical shape and are widened out from the valve portion 83, an axial safety mechanism is given for the compression spring 6 on the shoulder 84. In this manner, the assembly of this valve 9' is facilitated. The lower valve portion 85 is again partly ball-shaped I construction and has a maximum diameter that corresponds to the maximum diameter of the shoulder 84. The valve portion 85 can also be constructed in a conical shape. The greater diameter of the shoulder 84, or as the case may be, the lower valve portion 85, is smaller than the greater diameter of the upper valve portion 83. Accordingly, the lower valve portion 85 has a smaller valve diameter than the upper valve portion 83, so that the upper valve seating 41 has a greater diameter than the lower valve seating 42. The upper valve seating 41 is traversed axially by the rod 2. The resulting annular area 81 (
The remainder of the valve control mechanism of
The front face or surface 16 of the set piston 15 is provided with a choke cross-section 48, which is diametrical in the preferred embodiment and which, in cross section, is constructed as a three-corner recess. Also, the opposite front face or surface 28 of the set piston 15 is provided with a choke cross section 49, which, likewise, preferably is constructed, in cross section, as a three-corner, diametric recess. As in the previous embodiments, the front surface or face 28 of the set piston 15 is fitted against the rod 19, which, like the previously described embodiments, has a smaller cross-section than the front face or surface 28 or the set piston 15. The cupping rod 20 and the valve shaft 22 are shifted across the rod 19, in the manner described.
The supply line 10 empties in an annular channel 50, which is provided in the wall of a piston space or chamber 51. A wider annular channel 52 in the wall of the piston space or chamber 51 is provided in the cylinder area or chamber 17. This annular channel 52 is connected to the tank line 12 by a return line 53. The cylinder space or chamber 17 is connected to a return line 55 by a shunt line 54, the return line 55 separating the shunt line 54 from the return line 53 and which opens in the direction of the shunt line 54.
Upon the opening of the intake/exhaust valve 30, the piezo element 1 becomes charged. The rod 2 will be shifted across the lever 33, whereby the valve element 3 is lifted from the seating 41 and is brought to rest on the opposite valve seating 42. In this manner, the pressure line 7 is opened, so that the hydraulic medium can flow across the valve chamber 4, the supply line 10, the transverse borehole 46 and the return valve 47 in the surge chamber 14. When the valve element 3 lies against the valve seating 42, the connection to the tank line will be closed. The hydraulic medium arrives at the annular channel 50 through the supply line 10, the annular channel 50 closed by the set piston 15 next. The set piston 15 is shifted below by the hydraulic medium in the surge chamber 14. In contrast to both previous embodiments, hydraulic medium is found in a lower cylinder space or chamber 17. It is emptied into the tank line 12 by means of the shifting or displacement of the set piston 15 across the annular channel 52 and the return line 53. The front face or surface 38 is found next to, but spaced from, the annular channel 52. Passage of the set piston with its front faces or surface 28 to the leading edge 57 of the annular channel 52, the choke cross-section 49 in the front face 28 begins working together with the annular channel 52. As the recess 49 in the direction of the front face 28 continuously enlarges, the downward motion of the set piston 15 accedes toward the passage of the leading edge of the annular channel 5. Due to the increasingly smaller choke cross-section and the closed return valve 55 a throttle effect is created, which leads to a damping effect from the downward motion of the set piston 15. As a result of the continual narrowing of the cross section of passage for the hydraulic medium, a pressure in the medium in the cylinder space or chamber 17 is built up, which works against the downward motion of the set piston 15 and so the damping effect is brought about through the reduction of speed. The return valve 55, which is connected to the cylinder space or chamber 17 by the shunt line 54, closes against the return line 53 and therefore the tank line 12.
To close the intake/exhaust valve 30, the piezo element 1 is again rendered currentless and thereby shortened. The valve element 3 is shifted or displaced from the valve seating 42 by the compression spring 6 in the described manner and pressed against the valve seating 41. In this manner, the pressure line 7 is closed off from the supply line 10. Likewise, the valve shaft 22 and the cupping rod 20 are shifted or displaced by means of the compression spring 21. The set piston 15 is carried along by the rod 19. The set piston 15 empties the hydraulic medium from the surge chamber 14 into the annular channel 50, through which the hydraulic medium flows, via the valve chamber 4, into the tank line 12. As soon as the front face of the set piston 16 passes over the leading edge 57 (
The described embodiments preferably show that the set piston 15 in both end positions is damped, or attenuated. In this manner, this valve control mechanism works very quietly. The remainder of the three-way valve 9" is constructed similarly to the previous embodiments. Also, with this valve control mechanism, the three-way valve 9", the set piston 15, and the piezo element 1 lie near one another in a space relationship in the valve housing 5. The valve housing 5 has therefore only a smaller or minor, height.
As
As
In the above-described manner, the lift of the set piston, and therefore the lift of the intake/exhaust valve 30 is unchangeable.
If the principles of engine management are followed, the set piston 15, and therefore also the valve 30, can be adjusted merely to the normal, or to other desired, lifts. Hereunto, both piezo elements 1, 1a will become charged and the piezo element 1a, after a specified time of lift, will be made currentless, so that the valve element 3a, by the force of the compression spring 6a, is moved into its closed position. In this manner, the pressure line is separated from the supply line 10. Concurrently, the piezo element 1 remains charged and, in this manner, the valve 3 is closed and the volume in the surge chamber 14 enclosed. Similarly to the previous examples, smaller fluid volume of the hydraulic medium flowed into the surge chamber determines the lift of the set piston 15, and therefore also the lift of the intake/exhaust valve 30, as the piezo element 1 again becomes charged and, in this manner, the line 63 to the tank 12 remains closed. The fluid volume found in the surge chamber 14 remains therefore enclosed, the valve 30 is opened a little wider, so that the a correspondingly smaller volume of a fuel-air mixture is received in the internal combustion chamber of the internal combustion engine.
Should the intake/exhaust valve 30 be closed, the piezo element 1 is switched to its currentless state. The compression spring 6 lifts the valve element 3 from his valve seating 66, whereby the hydraulic medium found in the surge chamber 14 can be displaced through the supply line 10 and the opened valve chamber 4 into the tank line 12.
As
The valve element 3a, likewise, is incorporated in a sleeve or bushing 70 (FIG. 16), whose lower end 71 is unflanged. The valve element 3a is pressed upwardly against the valve seating 72 by the compression spring 6a. The rod 2a axially penetrates the valve seating 72 and therewith, creates the requisite annular surface for the flow.
Both seating valves 9, 9a lie on both sides of the set piston 15 and axis-parallel to it. In this manner, the valve housing 5 has only a minimal height.
The cylinder chamber or area 17 is, as
To open the intake/exhaust valve 30, both piezo elements 1, 1a become charged. The magnitude of the lift of the set piston 15, and therewith of the intake/exhaust valve 30, depends on this, after which time as the opening of the intake/exhaust valve 30 begins, the piezo element 1a is no longer charge and therefore hydraulic medium can no longer flow into the surge chamber 14. In dependence on the charged state of the piezo element 1a, the lift of the intake/exhaust valve 30 can thereby be infinitely regulated or controlled.
For the closing movement of the intake/exhaust valve 30, a damper is to be provided, as illustrated by
With the described embodiments, the phase relationships of the opening and closing, respectively, of the intake/exhaust valve 30 can be changed, in contrast to a camshaft mechanism. It is therefore possible make the intake/exhaust valve 30-associated piezo elements charged or uncharged at the desired point in time. As described with reference to the embodiments shown in
The rods 2, 2a can be directly operated by the piezo elements 1, 1a, as is schematically represented in FIG. 6. However, it is also possible to provide a transmission lever 59 between the rod 2, 2a and the piezo element 1, 1a, respectively, in order to enlarge the opening and closing lift of the valve element 3, 3a with the default piezo lift. As schematically represented in the embodiment of
As in the embodiment of
As with the embodiment of
As in the embodiment shown in
According to the embodiment of
Both piezo elements 1, 1a line in separate casing areas 78, 79 (FIG. 15). The cylinder chamber or space 17 with the piston 15 is found in the area between both casing areas 78, 79. Through the ration of the lengths of the lever arms of the respective levers 33, 33a , the transmission radio is determined. In this manner, the minimal path of motion of the piezo-sided rods 58, 58a can be transmitted very simply in the required adjusted path of the rods 2, 2a , in order to reliably shift or displace the respective valve element 3, 3a with the required lift into the respective open or closed position.
The specification incorporates by reference the disclosure of German priority document 198 52 209.6 Nov. 12, 1998.
The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.
Tischer, Dieter, Trzmiel, Alfred, Maisch, Dieter, Panowitz, Herbert
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